1. Field of the Invention
The invention relates to medical tubing, and more particularly relates to an apparatus and method for applying adhesive to a section of the outer surface of a length of tubing.
2. Background of the Invention
Many medical procedures employ a length of flexible plastic tubing for delivering fluid to a patient or for withdrawing bodily fluids from a patient. Opposed ends of the tubing typically are placed permanently in communication with plastic fittings. The typical plastic fitting includes opposed proximal and distal ends and a passage extending between the ends. Portions of the passage adjacent the proximal end of the fitting are dimensioned to receive an end of the flexible plastic tubing. The distal end of the plastic fitting may be configured for placement directly in communication with a patient or for placement in communication with another fitting.
The connection between the end of the plastic tubing and the proximal end of the plastic fitting must prevent separation of the tubing from the fitting in response to pulling forces and also must achieve a fluid-tight hermetic seal. An adhesive typically has been employed for this one longitudinal side of the plastic tubing adjacent the end of the tubing. The end of the plastic tubing then is telescoped into the plastic fitting. The telescoping movement of the tubing is intended to urge the drop of adhesive completely into the annular space between the tubing and the fitting. This prior art procedure tends to cause some of the adhesive to be pushed into a bead on the tubing and externally of the proximal end of the plastic fitting. A sufficient accumulation of adhesive adjacent the proximal end of the fitting can affect the ability of external latches or shields on the fitting to perform properly. Additionally, it is difficult to assure that the adhesive has wicked properly into all areas between the plastic tubing and the fitting. Accordingly, it is difficult to ensure that a good hermetic seal has been achieved. A uniform distribution of the adhesive is difficult to achieve when the adhesive has a high viscosity. Hence, a low viscosity highly flowable adhesive typically is used for these purposes. This limits the selection of adhesives.
There also are disclosed attempts to secure plastic tubing to a fitting by first assembling the tubing to the fitting and then inserting adhesive into the annular space between the tubing and the fitting. The adhesive has been inserted, for example, with a small gauge needle and a low viscosity adhesive. This prior art approach again limits the types of adhesives that can be employed. Furthermore, this design is complicated and it is difficult to ensure that adhesive will flow uniformly into the annular space between a plastic tubing and the fitting.
The subject invention is directed to an apparatus and method for applying a thin coat of adhesive uniformly to an outer circumferential surface region of a section of plastic tubing. adjacent an end of the tubing. The apparatus comprises a pair of grippers that are selectively movable toward and away from one another. Each gripper may be formed from a metallic plate material with opposite front and rear faces and a tube-mating face extending between the front and rear faces. The front and rear faces of each gripper are spaced apart a thickness that is equal to or greater than the length of the tubing to which the adhesive is to be applied.
The tube-mating face of each gripper includes a concave adhesive transfer area located centrally between and substantially transverse to the front and rear faces. The concave shape of the adhesive transfer area in each gripper conforms to the external shape of the tubing and forms a common longitudinal axis with the grippers. Most tubing is substantially cylindrical, and hence the tube transfer areas define a concave semi-cylindrical surfaces. The dimensions of the adhesive transfer areas of the grippers are selected to enable the adhesive transfer areas to nest completely around the tubing without occluding the tubing.
The tube-mating face of each gripper further is characterized by front and rear counterbores extending into the respective front and rear faces of the gripper and symmetrically disposed around opposite ends of the adhesive transfer area. The counterbores, however, define a larger cross-sectional area than the adhesive transfer area.
The tube-mating face of each gripper further is characterized by a vacuum channel spaced from the adhesive transfer area and extending between the front and rear counterbores. The channels in the grippers are disposed to substantially register with one another when the grippers move toward one another.
Each gripper further includes an adhesive dispensing passage for delivery of adhesive to the adhesive transfer area of the gripper.
At least one gripper further includes a vacuum passage extending into communication with the vacuum channel and configured for communication with a vacuum source. Thus, the vacuum passage enables a low pressure to be applied to the channel and to the counterbores with which the vacuum channel communicates.
The apparatus is employed by delivering a controlled amount of adhesive through the respective adhesive dispensing passages and into the adhesive transfer areas. The flow of adhesive into the adhesive transfer areas may commence before the tubing is positioned between the grippers. The end of the tubing then is disposed between the grippers, and the grippers are moved to engage around opposite sides of the tubing. Thus, the tubing is engaged in the adhesive transfer areas, but without a tight gripping that could occlude the tubing. The adhesive preferably has already commenced flowing into the adhesive transfer areas when the grippers are closed around the tubing so that adhesive in the adhesive transfer areas is urged continuously and circumferentially around the section of the tubing to which the adhesive is to be applied. A vacuum is applied at the vacuum passage typically as the grippers are being closed around the tubing. The vacuum draws excess adhesive into the counterbores. The adhesive then flows from the counterbores through the channel and through the vacuum passage for collection and/or recirculation. The vacuum contributes to a uniform thin coating of adhesive around the outer circumferential surface of the tubing and further contributes to removal of excess adhesive from areas where an adhesive build-up could affect performance of the medical device to which the tubing is connected. Additionally, the adhesive removal steps may be carried out simultaneously with the adhesive application steps, and as a result additional cleaning steps are not required for removing excess adhesive.
There is a definite need in the art of adhesive application for improvements which can overcome problems which arise with prior art apparatus. The present invention is directed to overcoming these problems and fulfilling this need.